Recent measurements show that the Arctic’s sea ice extent in
January was the lowest ever in the satellite record, while the Antarctic
also saw lower than average ice coverage last month and a major ice
sheet there could be verging on instability.
The reports come at a
time when climate and polar researchers are investigating the potential
for heavy melting of ice sheets in the Arctic and Antarctic, and the
effects the loss of the ice could have on global sea levels.
According to the National Snow and Ice Data Center (NSIDC), January’s sea ice extent in the Arctic
averaged 5.2 million square miles,
down from the more than 5.6-million-square-mile average observed
between 1981 and 2010. The previous January low came in 2011; this
month’s mark was around 35,000 square miles less than that record.
The NSIDC, which researches and manages data about frozen
regions around the globe and their climates, says the drop varied
significantly from highs observed last January. The month’s unusually
high temperatures, which were caused by a strong negative phase arctic
oscillation – a
variance in air pressure between the poles and more central latitudes – led to the extremely low ice coverage throughout much of the Arctic region.
The Barents, Kara, and East Greenland seas
had “unusually low ice coverage,” and less than average coverage in the
Bering Sea and Sea of Okhotsk was observed. Ice in the waters
surrounding most of northeastern Canada and western Greenland were
reported to be “near average.”
This data continues a negative
decade-over-decade trend for January. The month’s average now sits at
negative 3.2 percent every decade based on data collected since 1979. It
also continues a trend of a less than 5.5-million-square-mile extent
reported in each consecutive January since 2005.
Despite what appears to be a consistent downward tendency in sea ice extent, a
recent study published in Geophysical Research Letters
suggests that the rate of Arctic ice loss may actually be slowing, at
least in the Atlantic. Even though the January trend is on a negative
trajectory, a tendency for more ice overall has been observed since
2005.
“There is little doubt that we will see a decline in Arctic
sea ice cover in this century in response to anthropogenic warming,”
according to the research letter. However, “internal climate variations
and other external forcings could generate considerable spread in Arctic
sea ice trends on decadal timescales.”
This research is supported
by analysis of Meridional Overturning Circulation in the Atlantic,
ocean patterns that circulate warm water to the Arctic and reduce the
ice extent. While the study focuses on the Atlantic’s circulation,
warming waters on the other side of the pole could persist.
Another recently released study
concerning an Antarctic ice sheet could
also point to changes in ice levels at that pole and its effects on
global waters. The West Antarctic Ice Sheet (WAIS), “considered the
major contributor to global sea level rise” tens of thousands of years
ago, could be primed to repeat history if the effects of greenhouse
gases partially melt or collapse the sheet. The WAIS could have added
several meters to seawater levels globally at a time when polar
temperatures averaged 2 degrees Celsius higher than they are today.
While
the researchers behind the study and its simulations are still not
certain about the effects of the potential WAIS melt, “Given a
business-as-usual scenario of global warming, the collapse of the West
Antarctic could proceed very rapidly and the West Antarctic ice masses
could completely disappear within the next 1,000 years,” according to
lead author Johannes Sutter of the Alfred Wegener Institute for Polar
and Marine Research.
The study estimates that the melt could lead
to a sea level increase of 3 to 5 meters, notwithstanding a the
potential for a rise of several more if ice at the Arctic pole also
continues to disappear.
5:12:00 PM
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